If you are among the people who always need to run the latest OS regardless of the config guide you probably found yourself in trouble going to OSX 10.9
On my system, I have zero to none performance in Resolve using Quicktime movies with embedded audio.
They don't play well in the media tab, but grading with them is even worse.
But there is a little trick.
After assembling your timeline , in my case from one QT file which has been chopped up by EDL , select all the embedded audio, right click on the biggest clip, click LINK two,three times to be sure it unlinked.
Then re-do the selection, but just the audio part again and use the CUT funktion to get rid of it.
Try playing it in the Color tab...should work fine now.
Then add your audio track from a WAV file back to that track and Voila, perfect playback, back to the old performance :)